Has anyone tested what the maxlift/duration cam could be used in a stock 440 with stealth heads without running into piston to valve clearance problems.

Many stock 440s have the pistons in the hole a ways. Any plans to replace the ootb springs and hardware?

Here's what I can tell you from first hand experience. Low compression motor home 440, stock out of the box stealths, stock rockers and pushrods. The Comp Cams XE275HL will slide right in, work great, and not break stuff! That's a 231/237 @ .50, .525 lift hydraulic. Mid 12's @ 3500lbs. easy and cheap.

I got away with a .488/.504 lift Crane hydraulic in my first hop up in 73. It was a bone stock 375 HP 440 in a 1969 Charger. That cam had a fairly ugly idle for a street cam, so it must have been about 286 intake duration at .006? So there is room, and if you stay under about .490 lift with a flat tappet hydraulic it should be OK. But you still need to check. There are just too many variables that can cause problems. If you are using a piston with valve notches, you have a lot of latitude. A fresh build with zero deck and flat tops with no notches, better check ANY cam.
Race cam lobe specs sometimes list the lobe lift at overlap TDC for two installed numbers, 106 and 110. For instance I have one with .169 at 106 degrees installed centerline,(this is a HUGE cam by the way) so if you multiply that .169 times the rocker ratio, then calculate the beginning distance between the valve head and the piston top you have a vague idea of how deep you need to go with the notches on a big cam. Most intake valves will be closest at about ten degrees after TDC, exhausts about 10 degrees before TDC. But I still take readings for both lobes from 10 before through 10 after just to be sure I found the tightest spot.